Extração sólido-líquido e partição em baixa temperatura (ESLPBT) de Clorpirifós, Thiamethoxam e Deltametrina em maçã e análise por cromatografia gasosa

• Ano de defesa: 2008
• Autor(a) principal: Pussente, Igor Cabreira
• Orientador(a): Queiroz, Maria Eliana Lopes Ribeiro de
• Banca de defesa: Bellato, Carlos Roberto , Silva, Maria do Carmo Hespanhol da , Demuner, Antônio Jacinto
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Agroquímica
• Departamento: Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica
• País: BR
• Palavras-chave em Português: Análise de resíduos agrotóxicos; Alimentos; Maçã; Cromatografia gasosa
• Palavras-chave em Inglês: Pesticide residues analysis; Alimentos; Apple; Gas chromatography
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA
• Link de acesso: http://locus.ufv.br/handle/123456789/2074

The objective of this work was to optimize and validate a solid-liquid extraction and partition technique at low temperature (ESL-PBT) for analysis of the pesticides chlorpyrifos, thiamethoxam and deltamethrin in apple samples by chromatography. During optimization, ideal conditions for extraction of the pesticides of interest from the apple samples were determined by employing a factorial experimental setup. Composition of the extracted mixture, agitation type and time, ionic force of the aqueous solution and clean-up of the extract were evaluated to determine the best conditions for analysis of the compounds of interest. The apple samples and an extractor mixture in a single phase were agitated and frozen for approximately 8 hours. The matrix and frozen aqueous phase were separated from the still liquid (organic solvent) upper phase when lowering the temperature. This phase was submitted to a clean-up step and analyzed by gas chromatography, using bifentrin as an internal standard. The optimized technique consisted of preparing a solution of 3.0000 g of apple, 1.0 mL of an aqueous NaH2PO4 (0.2 mol L- 1), 6.5 mL acetonitrile, 1.5 mL ethyl acetate and the mixture was submitted to mechanical agitation for 30 minutes and then frozen. After this step, the supernatant was separated in a 10.0 cm column containing 2.0000 g of florisil and 1.5000 g of anhydrous sodium sulfate and the extract (10.0 mL) was analyzed by gas chromatography with an electron capture detector. The clean-up stage was necessary to minimize the interferences in the sample, but did not jeopardize the recovery percentages of the analytes of interest. The optimized method was validated by determining selectivity, detector linearity, detection and quantification limits, precision and accuracy. The results show that optimized ESL- PBT is selective and shows no interference peaks. This technique presented na average r2 value of 0.992 when analyzing the working range of 25.0 to 500.0 μg L-1. The detection and quantification limits of the established method for chlorpyrifos were 2.5 μg L-1 and 5.0 μg L-1, for the thiamethoxam pesticide were 5.0 μg L-1 and 15.0 μg L-1 and for deltamethrin were 10.0 μg L-1 and 20.0 μg L-1, respectively. Precision was divided in repeatability and intermediate precision. Repeatability presented coefficients of variation between 2.1% and 3.6% and intermediate precision obtained a maximum coefficient of variance of 6.6%. Accuracy showed coefficients of variation between 1.3% and 8.6% for chlorpyrifos, 5.1% and 9.2% for thiamethoxam and 5.1 and 16.2 for deltamethrin. The ESL-PBT showed to be efficient for analysis of the pesticide residues of interest in apple with recovery percentages greater than 70% and detection limits lower than the maximum limits of the residues (LMR) established by Brazilian legislation for these pesticides in this type of food. Quantification of pesticides in complex matrixes by gas chromatography can be affected by matrix components. In this work, the effect of the matrix was studied, employing analytical curves prepared in pure solvent and in apple extracts (control) for quantification of pesticides in apple extracts. The results showed that the matrix components can affects the quantification of the pesticides studied. However, a deeper study should be performed to better understand this phenomenon and propose suitable methods to reduce the matrix effect on quantification of pesticides in complex matrices by gas chromatography. The optimized and validated technique was applied in apple samples acquired commercial in the city of Vicosa, MG, Brazil. In the analyzed samples, the presence of the pesticide residue chlorpyrifos was found in the range of 0.25 to 0.30 μg L-1, concentrations inferior to those permitted by Brazilian legislation.